One example of conventional ball grid arrays is disclosed in JP-A-2004-111863. In the ball grid array, a plurality of semiconductor chips are mounted on one plane of an interposer, and solder balls functioning as ball terminals are arranged on the other plane of this interposer.
There are some cases that the above-described plural semiconductor chips are equipped with terminals for common functions, for instance, reset terminals related to serial communications and an oscillator of a microcomputer; terminals related to a power supply; A/D input terminals; terminals for input ports; test terminals, and the like. Accordingly, since the terminals for the common functions of the plural semiconductor chips are connected to common solder balls, a total number of these solder balls required to connect the ball grid array may be reduced so as to make the ball grid array compact.
However, the above-described ball grid array is employed where plural semiconductor chips are mounted on a common board. In other words, in the case that a single semiconductor chip is mounted on the interposer, this approach has not reduced the number of solder balls.
Thus, it is still desirable to provide a ball grid array which can be applied to such a case that a single semiconductor chip is mounted on an interposer, and which can be made compact, while a total number of ball terminals used to connect the ball grid array can be reduced.